Manufactured elongate wooden I-beams of the type to which the novel I-beam of this invention relates are well known in the art. Typical wooden I-beams each have continuous upper and lower flange or chord sections held in spaced apart relationship by being securely fastened to a central web section which extends along the full length of the beam so as to impart to it, in a cross-section, the "I" configuration. Fabricated wood I-beams use less wood and are usually lighter than regular sawn lumber used in similar applications such as floor joist and ceiling or roof rafters.
One of the more critical parameters governing the design of a wooden I-beam is the tension capacity of the bottom chord of the beam. Under normal uniform loading conditions, the requirement for the tension capacity is the greatest at the center of the span of the beam. The central region is therefore a critical region for strength design.
Still another important consideration is vibration performance. Means for improving the vibration performance of wooden I-beam floors, include the provision of bridging elements installed transversely between adjacent pairs of floor joists. However, conventional bridging elements such as cross-braces are not recommended for use with wooden I-beams, and solid blocking can be ineffective due to wood shrinkage. Other bridging systems have been developed, but are generally more costly to install.
In order to optimize ceiling height where wooden I-beams are employed as the joist, it is not uncommon for installers of duct work which must run transversely of the joist, to cut rectangular openings in the continuous web of the I-beams in order to permit the duct work to extend therethrough. Needless to say, the structural integrity and loading capability of I-beams cut open in this manner is compromised.
In U.S. Pat. 5,664,393, Veilleux, et al issued Sep. 9, 1997 there is provided a wooden I-beam having upper and lower chords and an open web structure joining the chords. The web is made up of a series of trapezoidal laminated panels which define a series of triangular spacing therebetween. These spacings permit the passage of electrical cable and piping therethrough, but not large sized objects such as ductwork as used for heating or air conditioning. Moreover, the Veilleux beam, as well as a box like beam having triangular openings in the sidewalls as disclosed in U.S. Pat. 4,228,631, Geffe, issued Oct. 21, 1980, is relatively expensive to construct when compared to conventional wooden I-beams.
While a portion of the web section of a regular wood I-beam may be cut out so as to accommodate ductwork, there is no provision for properly reinforcing the enlarged opening. Indeed, if an opening in the web is cut out in the field in order to accommodate ductwork or the like, one may attempt to reinforce the I-beam by nailing a vertical member to the sidewalls of the upper and lower flanges proximate one or both sides of the opening, or possibly positioning and nailing a vertical member to the opposing inner faces of the flanges along one or both of the sidewalls of the opening. This type of field modification is normally not followed because of the expense involved, and the necessity of obtaining requisite engineering approvals for such changes.